Four-cylinder, four-cycle, free piston, premixed charge compression ignition, internal combustion reciprocating piston engine with a variable piston stroke

Abstract

A four-cycle, four-cylinder, premixed charge compression ignition internal combustion reciprocating free piston engine with a variable piston stroke and a compression ratio that varies as needed to provide charge ignition, to offer the potential of higher efficiency, lower emissions, and multi-fuel operation. The engine does not have a crankshaft, and therefore does not provide direct rotary output. Instead its free pistons oscillate, in a manner similar to a two cycle free piston engine. For many applications, such as piston pumps and compressors, the engine provides an output directly driven by the oscillating pistons. In other applications, such as but not limited to use as a gas generator for a power turbine, the engine provides an indirect means of producing rotary power. When the engine is used with high-speed power turbines, the power turbine may be directly coupled to a high-speed alternator for electrical power output.

1. A fourcycle, free piston, premixed charge, compression ignition, internal combustion reciprocating piston engine with a variable piston stroke comprising:
 four cylinders constructed in a manner typical of reciprocating engines, each of said cylinders having two open ends; 
 at least one cylinder head affixed to said cylinders and configured to close one of said open ends of each said cylinder; 
 four pistons, each associated with and positioned for free movement within a different one of said cylinders; 
 two of said pistons coupled by a first mechanism to form a first piston pair so as to reciprocate together and the other two of said pistons coupled by a second mechanism to form a second piston pair so as to reciprocate together; 
 means of causing said first piston pair to reciprocate together, and said second piston pair to reciprocate together, all without a predetermined stroke length, and in a manner that allows a variable stroke and variable compression ratio, and wherein said reciprocation together of the said second piston pair is selected from a group consisting of reciprocation in the opposite direction to said first piston pair and reciprocation in the same direction as said first piston pair; 
 means of forming a premixed charge of fuel and reactant, said means of forming comprising means of controlling the size of said premixed charge and means of controlling the composition of said charge; 
 at least one intake valve associated with each of said cylinders which is configured to control the introduction of said premixed charge into the associated one of said cylinders; 
 means of conducting said premixed charge of fuel and reactant to each of said at least one intake valves; 
 said pistons each configured and dimensioned to create an intake stroke within an associated one of said cylinders wherein reciprocating motion of said piston away from said cylinder head allows said premixed charge to travel through said at least one intake valve and into the one of said cylinders associated therewith; 
 a combustion chamber formed within each of said cylinders, each said combustion chamber defined by said piston, the associated one of said cylinders, and said at least one cylinder head closing said cylinder; 
 said pistons each configured and dimensioned to also create a compression stroke within an associated one of said cylinders wherein reciprocating motion of said piston toward said at least one cylinder head continues until said piston compresses said premixed charge in said combustion chamber sufficiently to raise the temperature of said premixed charge to cause autoignition of said premixed charge and form combusted gases; 
 said pistons each configured and dimensioned to further create an expansion stroke within an associated one of said cylinders into which said piston is positioned for free movement wherein reciprocating motion of said pistons away from said at least one cylinder head allows said combusted gases in said combustion chamber to expand; 
 said at least one exhaust valve associated with each of said cylinders and configured to control the discharging of said combusted gases from said cylinder; 
 said pistons each configured and dimensioned to create an exhaust stroke within an associated one of said cylinders into which said piston is positioned for free movement wherein reciprocating motion of said piston toward said at least one cylinder head allows said expanded combustion gases to be exhausted through at least one said associated exhaust valve; 
 means of conducting said combustion gases as exhaust from said engine; 
 means for controlling the timing and causing of said intake valves and said exhaust valves to open and close during all of said cycles; 
 means of providing lubrication of said engine; 
 closure means adapted for sufficiently closing so as to contain lubricants and gas leakage past said pistons the one of said open ends of each said cylinder not closed by said at least one cylinder head; 
 means for starting said engine; and 
 means of providing cooling of said engine. 
 
   
   
     2. The engine as set forth in  claim 1  further comprising linearly oscillating means adapted for being driven by said reciprocating motion of said pistons and extracting power from said engine. 
   
   
     3. The engine as set forth in  claim 1  further comprising a pivot shaft connected to said reciprocating pistons and means adapted for being driven by said pivot shaft and extracting power from said engine. 
   
   
     4. The engine as set forth in  claim 1  wherein at least one of said engines functions as a gas generator, and further comprising turbine means driven by said exhaust from said gas generator and adapted for extracting power from said gas generator. 
   
   
     5. The engine as set forth in  claim 4  further comprising electrical generator means connected to said turbine means and adapted for extracting power from said turbine means. 
   
   
     6. The engine as set forth in  claim 5  wherein said turbine means comprises directly connected high-speed turbines and said electrical generator means comprises directly connected high-speed generators. 
   
   
     7. The engine as set forth in  claim 1  further comprising an electronic engine control having connections for said means for controlling the timing and causing of said intake valves and said exhaust valves to open and close during all of said cycles that are selected from a group consisting of electrical connections and electronic connections, said electronic engine control also having features selected from a group consisting of: an adaptive electronic control modules provided with the input of sensors and data, and which further comprises computational capability; an adaptive electronic control modules provided with the input of sensors and data, and which further comprises computational capability in the form of a microprocessor capable of determining the actual compression ratio that auto-ignited said premixed charge and using said computation in comparison to said input data to adjust and modify the timing and duration of opening and closing of said intake and said exhaust valves; an adaptive electronic control modules provided with the input of sensors and data, and which further comprises computational capability in the form of a microprocessor capable of determining the actual compression ratio that auto-ignited said premixed charge and using said computation in comparison to said input data to control fuel and reactant properties in said premixed charge; an adaptive electronic control module provided with input sensors and data input means, said adaptive control module further comprising computational capability in the form of a microprocessor capable of determining the actual compression ratio that auto-ignited said premixed charge and using said computation in comparison to input data provided by said data input means, said adaptive electronic control module also comprising output control means adapted for providing electrical and/or electronic output that maintains optimum engine operating conditions, said input sensors of said adaptive electronic control module having electrical and/or electronic connection to sensor input terminals of said electronic engine control, said input sensors also selected from a group consisting of: fuel flow sensors; fuel flow sensors providing fuel mass flow data; fuel and reactant characteristics sensors; fuel and reactant characteristics sensors providing reactant mass flow data; fuel and reactant charge temperature sensors; engine temperature sensors; engine throttle sensors; engine throttle sensors providing an engine operating set point in digital format; engine start and stop signal sensors; engine load sensors; position sensors sensing the position of said pistons; engine exhaust emission sensors; ignition sensors in each of said cylinders having features further selected from a group consisting of: piezoelectric pressure transducers, ion sensors, fast thermocouples and fast UV flame sensors, said data input means of said adaptive electronic control module having electrical and/or electronic connection to said electronic engine control, said data input means selected from a group consisting of: electronic data input and data storage capability, electronic data input and data storage capability including data on the anticipated compression ratio required to reach auto-ignition of the charge of fuel and reactant under varying ambient conditions, electronic data input and data storage capability including data on the anticipated compression ratio required to reach auto-ignition of the charge of fuel and reactant over the engine operating range, electronic data input and data storage capability including data on engine operating condition limitations, electronic data input and data storage capability including data on engine operating condition limitations in the form of a high speed data look up table, said output control means of said adaptive electronic control module having electrical and/or electronic connection to said electronic engine control said output control means selected from a group consisting of: intake and exhaust valve actuation devices, charge and reactant mixing and control devices, exhaust gas recirculation devices, engine coolant devices and engine lubrication devices. 
   
   
     8. The engine as set forth in  claim 1  further comprising variable valve actuation adapted for individually actuating said at least one intake valve and said at least one exhaust valve associated with each of said cylinders, said variable valve actuation comprising:
 at least one poppet intake valve, a return spring, seal and valve guide located within each said cylinder head intake port all constructed in a manner typical of reciprocating engines such that actuating said at least one poppet intake valve will effect gas exchange between said port and said cylinder; 
 at least one poppet exhaust valves, a return spring, seal and valve guide located within each said cylinder head exhaust port all constructed in a manner typical of reciprocating engines such that actuating said at least one poppet exhaust valve will effect gas exchange between said port and said cylinder; 
 at least one camshaft located above each said cylinder head and having cam lobes for each said poppet valve in said cylinder affixed thereto in such a manner to effect actuation thereof; 
 said cylinder poppet intake and exhaust valves each having a valve stem end typical of reciprocating engines that is located above said cylinder head; 
 means adapted for mounting said at least one camshaft over said cylinder intake and exhaust valves such that said camshaft lobes actuate respective ones of said poppet intake and exhaust valves by imparting pressure and linear movement of said valve stem ends as mounted ones of said camshafts are rotated or indexed to cause said poppet intake and exhaust valves to open and close; 
 means adapted for motorized rotation or indexing of said at least one camshaft that is selected from a group consisting of: electric drive motors; bi-directional stepper motors and bi-directional torque motors; 
 means adapted for electronic control of said motorized rotation or indexing means; 
 lubrication means for said at least one camshaft; and 
 lubrication means for said poppet valves.